It is known to use preformed inserts of foam material to insulate masonry building blocks, as is evidenced by U.S. Pat. Nos. 3,704,562 and 3,885,363. These inserts are formed by plastic molding companies, and generally are shipped to the masonry block manufacturer or to the building site for installation into the masonry blocks. This necessitates shipping and assembly costs which desirably should be avoided. In addition, undesirable storage charges are incurred; resulting from the need to inventory the inserts.
One approach to avoiding the above disadvantages associated with employing preformed plastic inserts is disclosed in U.S. Pat. No. 4,002,002, issued to Barnhardt, Jr. (hereinafter "Barnhardt"). In Barnhardt a low viscosity thermoset-type liquid foam material, such as urethane foam, is directed into a peripheral cavity formed between a shield insert and inner surfaces of cavities provided in the masonry block. In this system it is required that the shield be maintained within the cavity until the foam material sets up, or solidifies sufficiently to become form-sustaining without the support provided by the shield.
There are several disadvantages to using urethane foam or similar thermoset-types of liquid materials to insulate masonry blocks. With respect to urethane foam, a shrinkage problem often is encountered as the foam solidifies. This can create gaps or voids in the insulating layer thereby impairing the insulating function. Modern block plants can produce three 8-inch blocks every 8 or 9 seconds. In order to employ Barnhardt's method to insulate these blocks at the rate they are produced, excessively high manpower requirements would be needed to fill the cavities with the foaming ingredients. In addition, a large number of shields would be needed since they must be maintained with the blocks until the foam solidifies. Moreover, excessive storage space needs to be provided to accommodate the blocks as the foam is solidifying. A further negative resides in the fact that utilizing urethane foam is quiet costly; being considerably more expensive than utilizing expandable polystyrene as the insulating material.
For all of the above reasons the in-situ formation of an insulating layer with a low viscosity, thermoset-type foam, such as urethane foam, is not desirable. In fact, to the best of applicant's knowledge, the technique disclosed in the Barnhardt patent has never been successfully commercialized.
As indicated above, it is known in the prior art to mold preformed beaded polystyrene inserts for subsequent inclusion in the internal cavities of masonry blocks. A typical expandable polystyrene (EPS) molding facility will employ the following techniques to manufacture these preformed inserts:
1. Raw material is purchased in a bulk density of 38-40 pounds per cubic foot. PA0 2. The raw material is pre-expanded to a desired end product density in the range of from about 1.0 to about 1.5 pounds per cubic foot. PA0 3. After the pre-expanded beads are aged for a suitable period of time they are conveyed by air to a molding machine. PA0 4. Matched metal molds, usually of aluminum, are mounted in the molding machine to receive the pre-expanded beads. PA0 5. The pre-expanded beads are fed into cavities defined by the matched molds by either slide runner fill systems or E.P.S. fill guns. The molds are either provided with proper machined venting, or are crack-filled to permit air to excape during this filling operation. PA0 6. Steam is injected into the cavities through suitable passages in both mold halves to fuse the beads together into a coherent mass. PA0 7. Since the fused particles will continue to expand while hot, it is desirable, if not necessary, to cool the molds before they are opened to remove the end product. PA0 8. When the end product is adequately cooled it is removed from the mold, packaged, inventoried and shipped. PA0 1. Cement, water and other necessary aggregates are premixed and dumped into a hopper above the masonry block forming machine. PA0 2. A proper amount of material is then fed into the block molds, and the machine is cycled to form the molds in the "green" (freshly molded) state. These blocks are uncured and are quite fragile. PA0 3. The "green" blocks are conveyed to racks and cured in a kiln. PA0 4. As the "green" blocks are conveyed to the kiln, cured blocks are automatically taken from the racks and conveyed to a cubing (i.e. stacking) station. PA0 5. The cubes of masonry blocks are then ready for delivery to the building site. PA0 positioning a male plug member within the internal cavity of the building block with at least one peripheral wall of the plug member spaced from at least one interior surface of the cavity to form a peripheral compartment; PA0 directing the polymer particles into the peripheral compartment; PA0 injecting steam, under pressure, into the peripheral compartment to expand said polymer particles and cause them to fuse together into a self-sustaining, insulating layer in close conformity with each interior surface of the peripheral compartment, and, while injecting steam under pressure into the peripheral compartment; PA0 applying a counteracting, inwardly directed external force to exterior surfaces of at least two opposed walls of the block, an insulating layer being expanded into close conformity with the interior surface of at least one of said opposed walls; PA0 terminating the steam injecting step; PA0 removing the male plug member from within the internal cavity of the building block; and PA0 removing the external force applied to the opposed exterior surfaces of the block.
It is typical to employ molding cycles in excess of ninety (90) seconds to fabricate the preformed polystyrene inserts. This high cycle time is required primarily because of the necessity to cool both mold halves prior to opening the mold in order to cool the preformed inserts sufficiently to prevent undesired post-expansion.
A typical modern concrete block molding facility will employ the following techniques to manufacture masonry blocks:
In a typical production operation three 8-inch blocks are produced every 8 to 9 seconds.
It should be apparent from the above discussion that there is a significant difference between the cycle time necessary to mold preformed inserts from expandable polystyrene, and the cycle time necessary to form masonry building blocks. Therefore, even though expandable polystyrene is a highly desirable material for insulating masonry building blocks, no one has ever thought it possible, prior to the instant invention, to marry the polystyrene molding technology with the significantly different masonry block fabrication technology and come up with a commercially feasible and economical technique for the in-situ molding of expandable polystyrene layer(s) on surfaces of masonry building blocks.